“The answer to that is not only drunk, but deliberately so,” O’Toole said, laughing.

That was certainly the case on 1962’s “Lawrence of Arabia.” O’Toole’s co-star Omar Sharif once told me a story about the two of them getting sloshed before shooting the scene where they raid Aqaba. The actors had to mount camels and lead 400 extras in a furious mile-and-a-half charge.

Terrified he’d fall off, Sharif was thinking of tying himself to the camel.

“What are you going to do?” he asked O’Toole.

“Well, I’m going to get drunk,” O’Toole responded.

“Well, I am, too,” Sharif said, and the two knocked back several glasses of brandy and milk.

When the movie came out, Time magazine marveled at O’Toole’s “messianic fury” in the scene.

Asked about it by an interviewer, O’Toole said, “ ‘Messianic fury’? I was pissed as a pillow!”

O’Toole once burnt his index finger to the bone, with no memory of how it happened.

“Drinking was part of the role he was creating for himself,” Sellers said. “He played up being Irish, and drinking was a part of that, but though he had an Irish passport he was in fact born in Leeds [in England].”

O’Toole and his acting pals, including Richard Burton and Richard Harris, were also rebelling against the kind of refined, sometimes effete theatricality of writers and performers like Terence Rattigan and Noël Coward.

“They were the angry young men,” Sellers said of O’Toole’s posse. “They were saying, ‘We’re not like these theater blokes. We drink and shag women.’ ”

Stories of benders abound in the book. O’Toole once took his understudy in a play, an unknown by the name of Michael Caine, out for a drink. They woke up in a strange apartment in the company of two women they didn’t know. Sunday was going to be a long day, they thought — until they were told it was Monday. They also discovered they’d been banned from the restaurant where they had been drinking.

O’Toole on the set of “Lawrence of Arabia,” in 1962.Everett Collection

“Never ask what you did,” O’Toole told Caine. “It’s better not to know.” Caine heeded the advice but never drank with him again.

No matter. There were plenty of others who would. Harris formed a group called Alcoholics Unanimous. If you didn’t feel like drinking, you’d call up a “member” who would persuade you to join him for a drink.

High jinks included brawling in pubs, throwing up in the lobbies of fancy hotels, and urinating on stage during a play. O’Toole once burnt his index finger to the bone, with no memory of how it happened.

“They couldn’t get away with what they did today, not with social media,” said Sellers. “What sounds mythic, even funny, would look boorish and ugly on Facebook.”

O’Toole managed to keep it together for a time, starring in such first-rate movies as “Becket,” “The Lion in Winter,” “The Night of the Generals” and “The Ruling Class.”

But the alcohol ate away at his stomach, and by the end of the ’70s, his doctor told him one more drink could kill him. He underwent several operations and in later years would show off the ugly scars lacerating his abdomen.

O’Toole gave up drinking for 10 years, although he replaced the booze with cocaine and marijuana, which he grew in his garden in Ireland.

O’Toole is honored at the TCL Chinese Theatre in Los Angeles in 2010.AP

His behavior was erratic, leading to a catastrophic production of “Macbeth” at the Old Vic in 1980. O’Toole demanded that the set be drenched in blood — so much blood that the actors slip-slided all over the stage. One night he went onstage wearing sweatpants and sneakers.

The reviews were the kind that could drive an actor to suicide, though O’Toole managed to keep his sense of humor. “What could I do? My shaver is electric so I could not cut my throat,” he said.

O’Toole died in 2013 at the age of 81. He was unrepentant till the end, even allowing himself a pint of beer now and then. A few years before, a BBC interviewer asked if, at his advanced age, he had any message to pass on.